From a physiological standpoint, all sounds that hamper normal rest, study, and work of people or interfere with sounds that people want to hear are noises. In this sense, noises have a very wide range, and e.g., sounds made by cars in the streets, voices in a quiet library, machine sounds on a construction site, and loud sound of a neighbor's television are all noises.
Commonly, the strength of noise is measured by decibels (“dB”), and impact of noise on signal is measured by the signal to noise ratio (S/N). As described above, possible sources of noises include airplanes, cars, factories, construction sites, and the like.